01. Experimental/Computational Fluid Dynamics

A synthetic jet is a typical example of an excited or unsteady jet. Synthetic jets are formed by repeated ejection and suction to create a flow with a real downstream flow rate due to entrainment. The generation limit of a synthetic jet can be expressed in terms of a dimensionless stroke, which is determined based on the representative speed, frequency, and slot width. A recent study investigated the relationship between the phase difference of the velocity fluctuation and the generation limit of the jet flow by creating a situation in which the jet flow was interfered with by generating synthetic jets from multiple adjacent slots. The study revealed that jet flow formation is not observed when the dimensionless stroke length is large, and a phase difference exists in the velocity fluctuation. The oscillation conditions for jet flow interference are, in most cases, limited to a phase difference of π in the velocity variation, and much remains unknown about the relationship between dimensionless stroke length and phase and jet flow generation when two synthetic jets interfere. In this study, we focused on the generation limits of synthetic jets. We attempted to elucidate this using an experimental method under the condition that the phase difference of the velocity fluctuation between adjacent multiple slot exits is zero. In this study, the distance between the two slot exits was considered as a parameter. The main results are as follows: When the relative slot spacing based on the slot widths is small, the representative length is the sum of the two slot widths. By doing so, the generation limit can be treated as if it were a single synthetic jet. When the relative slot spacing is large, the generation limit of a single synthetic jet is valid.